(a) Field of the Invention
Leakage of ship's oil or spillage of oil tanker cargo has increased in severity and frequency over the years. This is a result of ships gradually changing from coal to fuel oil for propulsion. The increase in oil spillage can also be attributed to a greater number of tankers having a larger capacity to carry oil, which, in turn, allows a greater quantity of oil to be shipped from distant oil fields and refineries, leaving a higher probability of oil spillage.
Large oil spills can cause permanent damage to the aquatic environment. The oil also gets into the aquatic food chain, and directly contaminates fish and shellfish. Estuaries, where various species breed, also important links in the food chain, have become contaminated. In addition, fish, water foul, and mammals living in the water can face damage and destruction.
There is also the potential for damage to the sea shore, such as beaches and waterfront property. This is due to the accumulation of heavy weight oils, such as crude oil. The only effective way to deal with this situation is to attempt to minimize the quantity of oil spilled.
(b) Description of the Prior Art
Various techniques have been devised for controlling the spread of oil spills and removing them from the surface of the water. The following techniques may be relevant to various aspects of the present invention.
Towed barges or self propelled vessels fitted with scoop type skimming structural arrangements have been brought into the region where the spill has occurred and are used to skim the water surface, removing oil therefrom. Depending on the quantity of the oil spilled, the recovered oil can either be stored temporarily on board the recovery vessel or pumped directly to another holding means.
Another method, that can be incorporated with the first method or used by itself, is to deploy a flotation barrier for confining the spread of oil. Aprons of varying depth are attached to the flotation barrier to form a dike that blocks or at least retards the oil from spreading. See Blockwick, U.S. Pat. No. Re 28,966.
Both the first and second techniques require transporting the required containment and recovery equipment to the site of the spill. For spills that occur near coastal areas, a delay of hours to days can be experienced in getting the equipment to the site of the spill. Rapidly shifting tides, currents, and wind driven seas can quickly spread the oil over large areas, rendering it even more difficult or impossible to contain and remove the oil before widespread permanent damage has occurred.
Oil spillage in the open ocean and seaways is essentially impossible to combat, because rescue equipment typically cannot be brought to the site of the spill before the oil is essentially dispersed. Since speed of action is required in minimizing the spread of an oil spill, equipment not immediately available at the spill site cannot be of assistance for this problem.
One prior art attempt which has addressed the aforesaid problem is disclosed in Bouvier, U.S. Pat. No. 4,249,834, which proposes carrying an oil spill containment device, storage tank, pumps, etc., on board the vessel. However, the device proposed by Bouvier is not believed to have been adopted in practice due to the fact that it is impractical to install on a ship, since it hangs over the side and is subject to damage alongside piers and is unprotected from the open ocean environment.